1. Field of the Invention
The present invention relates to methods and apparatus for modulating the temperature of a modulated differential scanning calorimeter ("MDSC") by modulating characteristics of gas in thermal contact with the sample and/or the reference in the MDSC.
2. Background of the Invention
Modulated differential scanning calorimetry and differential thermal analysis are described in the above-referenced patents and patent applications, which are hereby incorporated by reference. Briefly, differential scanning calorimetry ("DSC") is an analytical technique in which the heat flow associated with a chemical, physical or crystallographic transformation in a material is measured as a function of temperature and time (and possibly pressure). Modulated differential scanning calorimetry is an advanced technique, in which the total heat flow signal is obtained as the temperature of the sample and/or reference is heated according to a basic heating rate upon which a temperature oscillation has been superimposed. The total heat flow signal can then be deconvoluted to obtain one or more deconvoluted signals representative of, e.g., the rapidly-reversible and/or nonrapidly-reversible components of the heat flow.
Major advantages of MDSC include (1) the ability to separately measure one or more components of the total heat flow signal; (2) an improved ability, compared to conventional DSC, to measure transformations or other thermal events which are overlapped in temperature and/or in time; and (3) improved resolution by allowing for the use of a relatively slow underlying heating rate.